1. Field of the Invention
The present invention relates to a process for converting the representation of a video image between two coding systems. More specifically, the invention relates to a process that makes it possible to convert the representation of a video image between two coding systems in which the two respective sets of parameters are deduced from one another by means of a matrix transformation.
The invention can be applied, for example, to the conversion of images between the RGB and YCbCr standards.
2. Description of the Related Art
When an image is sent through a network, for example of the Internet type, the image can be compressed by an algorithm in accordance with ITU standard H261. The image is coded according to the YCbCr coding system (Y=luminance, Cr=the difference between the red component and the luminance, Cb=the difference between the blue component and the luminance) defined in recommendation 601 of the CCIR (International Radio Consultative Committee). When the image is retrieved in an operating system, for example of the "WINDOWS" type, the image is coded according to the RGB standard (R=red, G=green, B=blue). The two sets of parameters of the two coding systems are deduced from one another by means of a matrix transformation. Thus, the conversion of the parameters from one coding system to the other requires, for each pixel of the image, a number of calculations that are very costly in terms of machine time.